1. Field of the Invention
The present invention relates to an apparatus for observing a surface of a material, finely machining the material and recording and reproducing information by a technique of a scanning tunneling microscope (STM) or the like.
2. Related Background Art
The observation, evaluation and fine machining of a semiconductor or high molecule material in the order of an atom or a molecule by using the STM technique (E. E. Ehrichs, 4th International Conference on Scanning Tunneling Microscopy/spectroscopy, '89, S13-3) and applications thereof to various fields such as a recorder have been studied.
Among others, a demand for a large capacity recorder for computer calculation information and image information is increasing more and more, and size reduction of the recorder is desired because of the fact that a size of a microprocessor has been reduced and a computing ability of the microprocessor has been improved. In order to meet the above requirements, a recording and reproducing apparatus has been proposed which records information on a recording area of 10 nm.sup.2 at minimum by applying a voltage from a transducer having a tunneling current generating probe mounted on drive means to finely adjust spacing to a recording medium in order to change a work function of a recording medium surface, and reads the information by detecting a change in a tunneling current due to the change in the work function.
The above transducer is very effective means for not only the recorder but also material evaluation and fine machining of a nanometer order.
In the above apparatus, it is necessary to adjust spacing between a probe and a medium so that processing is always performed at proper spacing. For example, in the recording and reproducing apparatus described above, if the drive means malfunctions to separate the probe from the medium more than required, the information cannot be written onto the recording medium. If a similar malfunction occurs in the information record mode, the information is not correctly read and all signals read from the recording medium may be "0". Such malfunction may occur not only in the spacing adjustment but also when the probe is scanned parallel to the medium surface. In the past, when such malfuction occurs, the written information is read by another apparatus for analysis or the read information is checked if it is not normal for a predetermined time period in order to detect the malfunction. Accordingly, a long time is taken to detect the error and it is time consuming.